JP3496156B2 - Variable control of electroosmotic and / or electrophoretic force via electric force in a fluid containing structure - Google Patents

Abstract

In a microfluidic system (partially shown by element 178 in the figure and elements thereupon) using electrokinetic forces, the present invention uses electrical current or electrical parameters, other than voltage, to control the movement of fluids through the channels of the system. Time-multiplexed power supplies (200 and 202) also provide further control over fluid movement by varying the voltage on an electrode connected to a fluid reservoir of the microfluidic system, by varying the duty cycle during which the voltage is applied to the electrode, or by a combination of both. A time-multiplexed power supply can also be connected to more than one electrode for a saving in cost. <IMAGE>

Description

DETAILED DESCRIPTION OF THE INVENTION CROSS REFERENCE TO RELATED APPLICATION This application is a continuation-in-part of US patent application Serial No. 08 / 678,436, filed July 3, 1996. The entire application is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION There is increasing interest in the manufacture and use of microfluidic systems for the acquisition of chemical and biochemical information. Techniques commonly associated with the semiconductor electronics industry, such as photolithography, wet chemical etching, are also used to fabricate these microfluidic systems. The term “microfluidic” is generally manufactured on the micron or sub-micron scale (eg, having at least one cross-sectional dimension of about 0.1 μm to about 5 μm).
(As having a range of 00 μm), a system or device having channels and chambers. An initial consideration of the use of planar chip technology for the fabrication of microfluidic systems is given in Manz et al. Trends in Anal. Chem. (1990) 10
(5): 144-149 and Mand et al. Avd. In Chromatog.
(1993) 33: 1-66. These describe the fabrication of fluidic devices as described above, in particular microcapillary devices, on silicon and glass substrates.

There are countless applications of microfluidic systems. For example, 19
International patent application WO 96/0454 published on Feb. 15, 1996
7 describes the use of microfluidic systems for capillary electrophoresis, liquid chromatography, flow injection analysis, and chemical reactions and synthesis. A related patent application, US Application No., entitled "High Throughput Screening Assay System for Microscale Fluid Devices," filed by J. Wallace Parce et al. On June 28, 1996 and assigned to the present assignee It discloses a wide range of applications of microfluidic systems in rapidly assaying the effects of compounds in various chemical systems, and preferably biochemical systems. "Biochemistry"
The phrase generally refers to a chemical interaction involving a type of molecule commonly found in living organisms. Such interactions include a variety of catabolism and assimilation reactions that occur within the manufacturing system, including enzymatic reactions, binding reactions, signaling reactions and other reactions. Biochemical systems of particular interest include, for example, receptor-ligand interactions, enzyme-substrate interactions, cell signaling pathways, model barrier systems (eg, cell or membrane fractions) for bioavailability screening. Transport reactions, and various other common systems.

There are numerous method descriptions for transporting and directing fluids such as samples, analytes, buffers and reagents within these microfluidic systems or devices. 1
In the method, the fluid in the microfabricated device is
It is moved by mechanical micropumps and valves within the device. Published British Patent Application No. 2 248 891 (10/18
/ 90), published European patent application No. 568 902 (5/2 /
92), and U.S. Pat. Nos. 5,271,724 (8/21/91) and 5,277,556 (7/3/91). Also, Miyaz
See also U.S. Pat. No. 5,171,132 (12/21/90) to aki et al. In another method, acoustic energy is used to move a fluid sample within a device due to acoustic streaming effects. Published No
See PCT Application No. 94/05414 to rthrup and White. A straightforward method is to move the fluid within the device by applying external pressure. See, eg, Wilding et al., US Pat. No. 5,304,487.

Yet another method uses an electric field and the resulting electrokinetic force to move fluid material through the channels of a microfluidic system. For example, the published European patent application No. 1 by Kovacs
376 611 (12/30/88), Harrison et al. Anal. Chem. (199
2) 64: 1926-1932 and Manz et al., J. Chromatog. (1992).
593: 253-258, as well as Soane U.S. Pat. No. 5,126,022. Dynamic power has the advantages of direct control, fast response and simplicity. However, there are still some drawbacks to this method of operating microfluidic systems.

The device uses a network of channels in a substrate of electrically insulating material. The channel connects a plurality of fluid reservoirs that contact the high voltage electrode. Specific voltages are simultaneously applied to the various electrodes to move the fluid material through the network of channels. Attempting to control the material flow in one channel without affecting the flow in another channel complicates the determination of the voltage value at each electrode in the system. For example, 4
In a relatively simple configuration with two channels intersecting in a cross and having reservoirs and electrodes at the ends of the channels, an independent increase in fluid flow between the two reservoirs merely increases the voltage difference between the two reservoirs. It doesn't matter. The voltages at the other two reservoirs must also be adjusted if they maintain their original flow and direction. Moreover, as the number of channels, intersections, and reservoirs increases, the control of fluid through the channels becomes more complex.

Also, the voltage applied to the electrodes in the device can be high (ie, to a level that supports thousands of volts / cm). Regulated high voltage sources are expensive,
Bulky, often inaccurate and requires a high voltage source for each electrode. Therefore, cost can be prohibitive in microfluidic systems of arbitrary complexity.

The present invention solves or substantially alleviates these problems of electrokinetic transport in microfluidic systems that simplify the control of the flow of matter through the channels of the system by using electrical parameters other than voltage. To do.
A wide range of applications such as chemistry, biochemistry, biotechnology, molecular biology, and many other fields, with high throughput and direct, fast and straightforward control over the transfer of substances through the channels of microfluidic systems. Microfluidic systems are possible.

SUMMARY OF THE INVENTION The present invention is directed to a plurality of interconnected capillary channels and a plurality of electrodes at different nodes of the capillary channels that create an electric field within the capillary channels to electrokinetically move substances in a fluid through the capillary channels. A microfluidic system having:
According to the present invention, a microfluidic system is provided by applying a voltage between a first electrode and a second electrode in response to an electric current between the first and second electrodes to move a substance therebetween. Is operated. The electric current may provide a direct measure of ion flow through the channels of the microfluidic system. Besides current
Other electrical parameters such as power may also be used.

Further, the present invention provides more accurate and efficient control of the power supply voltage on the electrodes of the microfluidic system by providing time multiplexing. The voltage to the electrodes can be controlled by changing the duty cycle of the connection of the electrodes to the power supply, changing the voltage to the electrodes during the duty cycle, or a combination of both. In this way, one power supply can accommodate more than one electrode.

The present invention also provides for direct voltage monitoring within channels in microfluidic systems. Conducting leads on the surface of microfluidic systems are
It has a width narrow enough to prevent electrolysis in some channels. The leads are also connected to a voltage dividing circuit provided on the surface of the substrate. Since the voltage divider circuit lowers the read voltage of the channel node, no special high voltage voltmeter is needed. The voltage divider circuit is also designed to minimize undesired electrochemical effects, such as gassing, oxidation / reduction reactions, by drawing negligible current out of the channel.

The invention described above may be subject to a number of different uses, such as the following, which are themselves inventive: the use of a substrate having at least one channel between two electrodes associated with the channel. By applying a voltage in response to the current at these electrodes,
Use, where the subject material is electrokinetically transported.

A use of the above invention, wherein the substrate has a plurality of interconnected channels and associated electrodes, wherein a voltage is applied to a given electrode in response to a current at the electrodes, Use, in which a substance of interest is transported along a predetermined route including one or more.

Use of a substrate having at least one channel for electrokinetically transporting a substance of interest by applying a controlled time-dependent application of an electrical parameter between electrodes associated with the channel. ,use.

Use of the above invention, wherein the electrical parameter is voltage,
Use, including current or power.

Use of an insulating substrate having a plurality of channels and a plurality of electrodes associated with the channels, wherein application of a voltage to the electrodes produces an electric field in the channels such that at least one conductive lead on the substrate Use, which can determine an electrical parameter at a channel position by extending to a position.

The use of the above invention, wherein the conductive lead has a width small enough so that a voltage of less than 1 volt, preferably less than 0.1 volt, is created across the conductive lead at the channel location.

An insulating substrate having a plurality of interconnected capillary channels, and a plurality of electrodes at different nodes of the capillary channel that create an electric field in the capillary channels to electrokinetically move substances in the fluid through the capillary channels, A first input terminal connected to at least one of the electrodes and receiving a controllable reference voltage;
A power supply having a mixing block having a second input terminal and an output terminal; connected to the output terminal of the mixing block,
A voltage amplifier having a first output terminal and a second output terminal, the first output terminal connected to the at least one electrode; and a voltage amplifier connected to the first output terminal of the voltage amplifier. A feedback block having an output terminal connected to the second input terminal of the mixing block and providing negative feedback for stabilizing the power supply.

Use of the above invention, in which the feedback block is also connected to the second output terminal of the voltage amplifier, the feedback block generating a first feedback voltage in response to the voltage at the first output terminal, A second feedback voltage in response to an amount of current delivered to the at least one electrode via one output terminal, the feedback block responding to a control signal, the first or second feedback. Use, having a switch for selectively stabilizing the power supply by voltage or current feedback by sending the voltage to a mixing block.

A power supply having a mixing block connected to at least one electrode of the microfluidic system and having a controllable reference voltage, a first input terminal, a second input terminal and an output terminal; connecting to an output terminal of the mixing block A voltage amplifier having a first output terminal and a second output terminal, the first output terminal being connected to the at least one electrode; first and second voltage amplifiers;
A feedback block connected to the output terminal and the second input terminal of the mixing block, the first feedback voltage being generated in response to the voltage at the first output terminal via the first output terminal. Negative feedback by generating a second feedback voltage in response to an amount of current delivered to the at least one electrode and sending the first or second feedback voltage to a mixing block in response to a control signal. A feedback block having a switch for selectively stabilizing the power supply in voltage or current.

Multiple interconnected capillary channels, multiple electrodes at different nodes of the capillary channel that create an electric field in the capillary channels to electrokinetically move substances in the fluid through the capillary channels, and connect to each of the electrodes A plurality of power sources, each power source capable of selectively supplying a selected voltage and a selected amount of current to the connected electrodes as a source or a sink. The substrate has a microfluidic system.

Brief description of the drawings   FIG. 1 is a representative view of a microfluidic system.

2A shows an example of channels in a microfluidic system as in FIG. 1; FIG. 2B represents an electrical circuit created along the channels in FIG. 2A.

FIG. 3A is a graph of output voltage versus time for a prior art power supply; FIG. 3B is a graph of output voltage versus time for a time multiplexed power supply according to the present invention.

4A is a representative diagram of a time-multiplexed voltage-operated microfluidic system according to the present invention; FIG. 4B is a block diagram illustrating a unit of the power supply in FIG. 4A.

5A is a representative diagram of a microfluidic system having a voltage monitoring node according to the present invention; FIG. 5B shows details of the voltage divider circuit of FIG. 5A.

Figure 6A is a block diagram of the power supply unit of Figure 4B;
6B is an amplifier block diagram of the DC-DC converter block of FIG. 6A.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a representative view of a portion of an example microfluidic system 100 operating in accordance with the present invention. As shown, the entire system 100 is manufactured within a planar substrate 120. Appropriate substrate materials are generally selected based on their suitability for the conditions present during the particular operation to be performed by the device. Such conditions include extremes of pH, temperature,
It may include ion concentration and application of an electric field. The substrate material is also chosen to be inert to the key components of the analysis or synthesis performed by the system.

The system shown in FIG. 1 has a series of channels 110, 112, 114 and 116 fabricated in the surface of substrate 102. As mentioned in the definition of "microfluidic", these channels typically have very small cross-sectional dimensions. Channels having a depth of about 10 μm and a width of about 60 μm operate effectively in the specific applications described below, although deviations from these dimensions are also possible. Microfluidic system 100
The subject material is transported through various channels of the substrate 102 for various purposes including testing, mixing with other substances, assays and combinations of these operations. The term "substance of interest" simply refers to a substance such as a compound or biological compound of interest. A compound of interest can be a compound, a mixture of compounds (eg, a polysaccharide), a small organic or inorganic molecule, a biological macromolecule (eg, a peptide, protein, nucleic acid, or organism such as a bacterium, plant, fungus, or animal cell or tissue). Extract made from biological materials), naturally-occurring or synthetic compositions, and the like.

Useful substrate materials include, for example, glass, quartz, ceramics and silicon, and polymeric substrates such as plastics. For conductive or semi-conductive substrates, an insulating layer is required on the substrate. This is particularly important for the system to use electroosmotic forces to move substances through the system, as described below. In the case of polymeric substrates, the substrate material may be rigid, semi-rigid or non-rigid, opaque, translucent or transparent, depending on the intended use. For example, devices with optical or visual detection elements are generally manufactured at least in part from transparent materials to allow or at least facilitate detection.
Alternatively, for these types of sensing elements, the device may be provided with a transparent window, for example made of glass or quartz. Further, the polymer substance may have a linear or branched skeleton, and may be crosslinked or not. Examples of particularly suitable polymer substances include, for example,
Polydimethylsiloxane (PDMS), polyurethane, polyvinyl chloride (PVC), polystyrene, polysulfone, polycarbonate, polymethylmethacrylate (PMMA), etc.

Substrate these channels and other microscale elements
Fabrication within the surface of 102 may be performed using any number of microfabrication techniques known in the art. For example, glass, quartz or silicon substrates may be manufactured using lithographic techniques in conjunction with methods well known in the semiconductor manufacturing industry. Photolithographic masking, plasma etching or wet etching, and other semiconductor processing techniques define microscale features within or on a substrate. Alternatively, a micromachining method such as laser drilling or micromilling may be used. Similarly, well known manufacturing techniques can be used for polymeric substrates. These techniques can be injection molding techniques or stamping techniques that can create large numbers of substrates, for example, by making large sheets of microscale substrates using rolling stamps, or high polymerization of substrates in microfabricated molds. Including molecular micro-casting technology.

In addition to the substrate 102, the microfluidic system 100 has additional planar elements (not shown) overlying the channeled substrate 102 to enclose the various channels.
ose) and fluidically sealed to form a conduit. Planar cover elements may be provided by a variety of means including thermal bonding, adhesives, or in the case of certain substrates such as glass or quasi-rigid and non-rigid polymeric substrates, such as natural adhesion between the two components. , Can be attached to a substrate. The planar cover element may further be provided with access ports and / or reservoirs for introducing various fluidic elements required for a particular screening.

The system 100 shown in FIG. 1 is also located and in fluid communication with the ends of channels 114, 116 and 110, respectively.
It has reservoirs 104, 106 and 108. A plurality of different target substances are introduced into the device using the channel 112 as shown. Thus, the channel 112 is in fluid communication with a source of a number of separate target substances, and the plurality of separate target substances are individually introduced into the channel 112 before being separated into another channel 110, for example for electrophoretic analysis. Introduced in.
The target substance is a fluid slag region with a predetermined ion concentration.
Transported through 120. These areas are separated by a buffer area (denoted as buffer area 121 in FIG. 1) having various ion concentrations. J. Wall, a related patent application, both of which have the title "Electronic Pipettor and Compensation Means for Electrophoretic Bias" and are assigned to the present assignee.
Ace Parce and Michael R. Knapp, US Application No. 08 / 671,986, filed June 28, 1996, and US Application 08 / 760,446, filed December 6, 1996, describe various configurations of slag. That is, the buffer regions of high ion concentration and low ion concentration in the transport of the target substance by electromotive force are explained. The entire contents of these applications are incorporated herein by reference for all purposes.

A voltage controller capable of simultaneously applying a selected voltage level (including ground) to each reservoir may be used to move material through the channels 110, 112, 114 and 116. Such a voltage controller can be implemented by using multiple voltage dividers and multiple relays to obtain selective voltage levels. Alternatively, multiple independent voltage sources may be used. The voltage controller is electrically connected to each reservoir via electrodes located or manufactured in each of the reservoirs 104, 106 and 108. See, for example, published Ramsey International Patent Application No. WO 96/04547. This entire document is hereby incorporated by reference for all purposes.

In addition to complexity, there are other problems with voltage control in microfluidic systems. FIG. 2A shows two reservoirs 132 and 134 contacting electrodes 133 and 135, respectively, and connected to the electrical leads shown as emerging from substrate 128.
Channel 130 between is shown. To make this example more realistic, channel 130 is shown connected to the other two channels 136 and 138. Operationally, reservoir 132 is the source of slag 120 containing the substance of interest. The slug 120 moves towards the reservoir 134, which acts as a sink. Channels 136 and 138
Provides a buffer region 121 for separating the slug 120 in the channel 130.

The different resistances of slug 120 and buffer region 121 in channel 130 create the electrical circuit symbolically shown in this simple example. The voltage V applied between the two electrodes 133 and 135 is Is. Where I is the current between the two electrodes 133 and 135 (assuming no current flows into 136 and 138) and R _i is the resistance of the different slugs 120 and buffer regions 121.

Voltage control systems are exposed to many factors that can interfere with the operation of the system. For example, contact at the electrode-fluid interface can be a source of problems. If the effective resistance of contact from the electrode to the fluid changes due to, for example, contaminants, bubbles, oxidation, the voltage applied to the fluid will change. When V is set on the electrode, the reduction in the surface area of the electrode in contact with the solution due to the formation of bubbles on the electrode results in an increase in resistance from the electrode to the solution. This reduces the current between the electrodes and, consequently, the electroosmotic and electrophoretic forces induced in the channel 130.

Other issues can also affect the current flow in the channel. Unwanted particles can affect the channel resistance by effectively changing the cross-sectional area of the channel. Again, when the channel resistance changes, the physical current flow changes.

Channel 136 connected to the illustrated channel 130 and
Also in other channels, such as 138, dimensional changes in the channel geometry in the substrate 102 can significantly impact the operation of the voltage control system. For example, the intersection node of channels 130, 136 and 138 may be X distances away from the electrodes (not shown) for the reservoir at the ends of channel 136,
It is assumed that it is separated from the reservoir electrode (not shown) at the end of 138 by a Y distance. Due to the slight lateral misalignment in the photolithography process, the distances X and Y will not be the same in a microfluidic system on another substrate. Voltage control must be recalibrated from substrate to substrate in order for fluid movement at crossing nodes to be properly controlled, a time consuming and expensive process.

To avoid these problems, the present invention uses current control in the microfluidic system 100. The current at a given electrode is directly related to the flow of ions along the channel that connects to the reservoir in which the electrode is located. This is in contrast to the requirement of measuring the voltage at various nodes along the channel in a voltage controlled system. Therefore, the voltage on the electrodes of the microfluidic system 100 is
Is set according to the current flowing through the various electrodes of the.
Current control is less sensitive to dimensional variations in the process of forming the microfluidic system on the substrate 102. Current control allows aspiration, valving, dispensing, mixing of target and buffer fluids in complex microfluidic systems
And the operation when performing the concentration is much easier. Current control is also suitable for mitigating unwanted temperature effects in the channel.

Of course, a direct metric of the ion flow between the electrodes (me
In addition to the current providing the asure), other electrical parameters related to the current may be used as controls for the microfluidic system 100. Power indirectly measures the current through the electrodes. Thus, the physical current (and ionic current) between the electrodes can be monitored by the power through the electrodes.

Even with the current control system described above, a high voltage must still be applied to the electrodes of the microfluidic system. The present invention provides a time-multiplexed power supply in order to eliminate the need to use a costly power supply that can produce a continuous and accurate high voltage. The time-multiplexed power supply can power more than one electrode, thus reducing the number of power supplies required for system 100.

FIG. 3A shows an example of the output of a high power power supply currently used in electrokinetic systems. The output is constant at 250 volts between the two electrodes regardless of time. In contrast, Figure 3
B indicates the output of a power supply operating according to the invention. To maintain a constant voltage of 250 volts, the output voltage is time multiplexed at 1000 volts with a 1/4 duty cycle. When averaged over time, the output of the time-multiplexed power supply is 250 volts, as indicated by the dotted line across the graph. As mentioned above, the output voltage of the time multiplexed power supply is also
It may be changed by changing the applied voltage, or by changing the duty cycle, or a combination thereof.

The flow of electroosmotic fluid is started and stopped on a microsecond time scale in a channel having the dimensions described herein. Therefore, at voltage modulation frequencies below 1 megahertz, the fluid exhibits irregular movement. This should not adversely affect the operation of the fluid as electroosmotic fluids have the nature of plug flow. Since most chemical mixing, incubation, and separation phenomena occur on a time scale of 0.1 to 100 seconds, much lower frequencies are acceptable in voltage operation. As a rule of thumb, to keep mixing or pipetting errors below 1%, the modulation period should be below 1% of the shortest switching phenomenon (eg, switching of flow from one channel to another). Is. Given a switching phenomenon of 0.1 seconds, the voltage modulation frequency should be above 1 KHz.

FIG. 4A shows a block of a multiplexed power supply system with two power supplies 200 and 202 and a controller block 204 for an example simple microfluidic system with channels 180 intersecting channels 182, 184, 186 and 188. It is a figure. Channel 180 has electrodes 190 and 191 respectively.
Ends in reservoirs 179 and 181 with. channel
182 terminates with a reservoir 183 having an electrode 193. The channel 184 terminates with a reservoir 185 having an electrode 195. The channel 186 terminates with a reservoir 187 having an electrode 197. The channel 188 is then terminated by a reservoir 189 having an electrode 199.

Power sources 200 and 202 are connected to different electrodes 190, 191, 193, 195, 197 and 199 of the microfluidic system. The power supply 200 is connected to the three electrodes 190, 193 and 195, and the electrode 202 is connected to the remaining three electrodes 191, 197 and 199. The controller block 204 includes each power supply 200 and
Connected to 202 to regulate the operation of these power supplies. For example, to control the movement of fluid through channels 182, 184, 186 and 188, electrodes 190, 191, 193, 195, 197 are used.
The voltages at 199 and 199 must be properly timed. Controller block 204 is power supply 200
And 202, the voltage on the electrodes is, for example,
As described above, it changes depending on the current.

Each of the power supplies 200 and 202 is combined into the unit shown in Figure 4B. The control unit 212 receives the control signal from the control block 204 and switches the switching unit 214.
Give instructions for the operation. The switching unit 214 is connected to the power supply unit 216 and connects or disconnects the power supply unit 216 to the connection electrode. That is, the switching unit 214 time-multiplexes the electric power from the power supply unit 216 between the connection electrodes. The power supply unit 216 is also connected to the control unit 212, which gives an indication of the variation of the output from the power supply unit 216 to the switching unit 214. In another configuration, this connection to the control unit 212 is necessary if the power supply unit 216 provides a constant voltage and the average voltage to the electrodes is changed by varying the connection duty cycle through the switching unit 214. Not done.

FIG. 6A is a block diagram of a power supply that can be used as the power supply unit 216 of FIG. 4B. Alternatively, if time multiplexing is not used, the illustrated power supply can be directly connected to the electrodes of the microfluidic system. The power supply may supply a stable voltage to the electrodes or may supply or sink a stable current.

The power supply has an input terminal 240 supplied with a controllable reference voltage of -5 to +5 volts, the magnitude of which is stepped up to several hundred volts at the output terminal 241. The input terminal is connected to the negative input terminal of the input calculation amplitude unit 230 via the resistor 227. The positive input terminal of the operational amplifier 230 is grounded, and the output terminal is connected to the negative input terminal via the feedback capacitor 220 and the resistor 228 which are connected in series. The output terminal is also connected to the input terminal of the DC-DC converter 231. Its second input terminal is grounded. The output side of the converter 231 steps up the voltage received from the amplifier 230 and is connected to the output terminal 241 of the power supply. The second output terminal of converter 231 is grounded through resistor 222.

The output terminal 241 of the power supply is also connected to ground via two series-connected resistors 221 and 223 forming a voltage divider circuit. The node between the two resistors 221 and 223 is
Connected to one input terminal of current / voltage mode switch 234. The node is also connected to the negative input terminal of feedback operational amplifier 232 via resistor 225. The negative input terminal is also connected to the output terminal of converter 231 via resistor 224 and to amplifier 232 via feedback resistor 226.
Connected to the output terminal of. The output terminal of amplifier 232 is also connected to the second input terminal of switch 234. The switch has an output terminal connected through a resistor 229 to the negative input terminal of the input operational amplifier 230.

The switch 234 responds to the signal on the control terminal 242. As shown in FIG. 6A, the switch 234 connects its output terminal to the output terminal of the feedback operational amplifier 232 or to the voltage dividing node between the two resistors 221 and 223. This connection determines whether the power supply circuit operates in voltage mode (connected to the voltage divider node) or current mode (connected to the output of the feedback operational amplifier 232). Note that resistor 221 is very large, about 15 MΩ, so the voltage at output terminal 241 can easily be fed back when the power supply is activated.

The circuit of FIG. 6A may be separated into different arithmetic blocks.
The operational amplifier 230, resistors 227-229 and capacitor 220 are part of the mixing block. The mixing block receives the controllable reference voltage V _ref and the feedback voltage at input terminal 240, described below, and produces an output voltage for the DC-DC converter 231, which is a combination of V _ref and the feedback voltage. The power supply operates at and near the reference voltage V _ref . Converter 231 shown as a voltage amplifier in FIG. 6B simply amplifies the voltage from operational amplifier 230. One output terminal of the voltage amplifier is connected to the output terminal 241 and the terminal of the resistor 221. The other output terminal of the voltage amplifier is connected to the ground via the resistor 222. Resistors 221-223 may be considered part of the feedback block, which further comprises resistors 224-226 and operational amplifier 232. Switch 234
Is also part of the feedback block and is connected to the second input terminal of the mixing block as described above.

Operationally, the mixing block has an operational amplifier 230,
The operational amplifier 230 is connected to the resistors 226 to 228 as a summing amplifier. When the capacitor 220 is in the feedback loop of the operational amplifier 230, the output voltage of the operational amplifier 230 is the sum (or difference) of the reference voltage V _ref and the feedback voltage from the switch 234, which is the integrated voltage over time. is there. Of course, the reference voltage V _ref and the feedback voltage may be selectively weighted by the value of resistors 229 and 227. Capacitor 220 and amplifier 230 also act as a filter to remove high frequency fluctuations from the power supply.

The output signal from operational amplifier 230 may be conditioned, eg, rectified or buffered, by additional elements (not shown). However, for the understanding of the present invention, the voltage received by the DC-DC converter 231, V _IN , can be considered to be the same as the output voltage of the operational amplifier 230. As shown in FIG. 6B, V _IN is amplified by gain factor A, and the amplified voltage AV _IN is produced on output terminal 241.

The feedback block has a voltage divider circuit formed by resistors 221 and 223 connected between the output terminal 241 and ground. The voltage at the node between resistors 221 and 223 is directly proportional to the voltage at output terminal 241. When switch 234 selects the voltage feedback mode in response to the signal on control terminal 242, the node voltage is fed back directly to the mixing block and operational amplifier 230. Negative feedback stabilizes the output at terminal 241. For example, if the voltage at terminal 241 is high, the feedback voltage is high. This causes the output voltage of operational amplifier 230 to drop, thereby compensating for the high voltage at output terminal 241. Output terminal 241
To monitor the voltage at the node, the node is further connected to an operational amplifier 251 configured as a single buffer and sends the feedback voltage to a monitoring circuit (not shown).

The feedback block further comprises an operational amplifier 232 and resistors 224-226. The resistors 224-226 are connected to form an operational amplifier 232 as a summing amplifier. One input to the summing amplifier is connected to the node between resistors 221 and 223. The second input is connected between the resistor 222 connected to ground and the second output terminal of the DC-DC converter 231. The summing amplifier measures the difference between the amount of current through series connected resistors 221 and 223 and the amount of current through converter 231 (total amount of current through resistors 222 and 224). In practice, the summing amplifier measures the amount of current flowing through output terminal 241. Thus, when switch 234 is set to the current feedback mode, the output from operational amplifier 232, which acts as a summing amplifier, is sent to the mixing block and the power circuit is connected to the microfluidic system via power terminal 241. It is stabilized at or near the amount of current flowing through the electrodes.

The output of the summing amplifier is further connected to an operational amplifier 250 configured as a single buffer, which sends the output voltage to a monitoring circuit (not shown). The monitoring circuit operates from the outputs of operational amplifiers 250 and 251 to output terminal 241.
With a measurement of the voltage at and the current through the terminals.
This further allows the monitoring circuit to determine and control the amount of power being supplied by the power supply circuit.

The ability of the above power supply to act as a variable source is
Allows the direction of fluid flow through the microchannels of the microfluidic system to be electronically altered. When all electrodes are connected to one or more of the power supplies described above, the operation of the microfluidic system is greatly enhanced and the desired movement of fluid through the channel network in the system is much more flexible.

Despite acting as a current control system, there is often a need to determine the voltage at a node in a microfluidic system. The invention further provides means for such voltage monitoring. As shown in FIG. 5A, electrical leads 160 are formed on the surface of the substrate 176 near the desired node 178 of the microfluidic system. Node 173 is at the intersection of channels 170 and 172 and 174 with reservoirs 169 and 171 at each end. The end of channel 174 has a reservoir 175 and the end of channel 172 (and the reservoir) are not shown.

The leads 160 are preferably formed by deposition of a conductive metal or alloy, preferably a noble metal such as gold on chrome or platinum on titanium used in integrated circuits. Lead 160 is 1μ by semiconductor photolithography technology
It may be defined with a width of less than m. To prevent electrolysis, the width of lead 160 in channel 170 is such that the voltage applied to the lead in channel 170 is always less than 1 volt, preferably 0.1.
Narrow enough to be less than a volt.

The voltages used in microfluidic systems are high.
A voltmeter that measures the voltage at channel node 173 directly via lead 160 must have a very high input impedance in order to be able to measure such high voltages. Such a voltmeter is expensive. Moreover, handling of substrates in microfluidic systems increases the potential for contamination. Such contamination can seriously affect the voltage (and electric field) required for proper operation of electrokinetic in the channels of a microfluidic system.

To avoid these problems and costs, leads 160 are connected to a voltage divider circuit 163, which is also formed on the surface of substrate 178. The output of the voltage dividing circuit 163 is
Carried by a conductive output lead 161. Circuit 163 is further connected to a voltage reference by conductive leads 162.

The voltage divider circuit 163 is shown in more detail in FIG. 5B and is formed by standard semiconductor manufacturing techniques with resistors 165 and 166 connected as a voltage divider circuit. Reed 160
Is connected to an input terminal of circuit 163, which is one end of a linear pattern of a high resistance material such as undoped or lightly doped polysilicon or alumina. The other end of the linear pattern is connected to the reference lead 162. The reference lead 162 is also formed on the substrate 168,
Connected to external reference voltage, probably ground. As shown for purposes of illustration, the voltage on lead 160 is divided at a ratio of 10: 1. Linear pattern is resistor 165 and resistor 1
It is divided into 66 and. Resistor 165 has nine times as many loops as resistor 166. That is, the resistance of resistor 165 is
9 times the resistance of. Of course, other ratios may be used, with a 1000: 1 ratio being typical. Two resistors 16
An output lead 161 connected between 5 and 166 connects to an external connection so that the low voltage can be read by a voltmeter. Cover plate has leads 160-162, voltage divider circuit
163 and protects the substrate surface from contamination.

While the above invention has been described in some detail for purposes of clarity and understanding, various changes in form and detail may be made by reading this disclosure without departing from the true scope of the invention. It will be apparent to those skilled in the art. All publications and patent documents cited in this application are incorporated by reference in their entirety for all purposes, to the same extent as if each publication and patent document were individually listed. It

Continuation of the front page (56) Reference JP-A-6-300736 (JP, A) JP-A-8-47251 (JP, A) JP-A-5-113829 (JP, A) JP-A-8-126311 (JP , A) Actual development Sho 64-10816 (JP, U) International publication 96/04547 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01N 27/447 JISST file (JOIS)

Claims (50)

(57) [Claims] 1. A plurality of interconnected capillary channels and a plurality of electrodes at different nodes of the capillary channel for creating an electric field in the capillary channel for electrokinetic movement of a substance in a fluid through the capillary channel. A method of using a microfluidic system having a plurality of electrodes for electrokinetically moving, the method comprising: applying a voltage to at least three of the electrodes with respect to other electrodes of the system. Including the step of simultaneously applying
The method, wherein the voltage causes a substance to move in and through one or more intersections of the plurality of channels of the system in response to a current in at least two of the at least three electrodes. 2. The method of claim 1, wherein the microfluidic system has more than three electrodes. 3. The step of applying a voltage includes the step of controlling the voltage so that the current becomes substantially constant.
The method of claim 2. 4. A plurality of capillary channels and a plurality of electrodes at different nodes of the capillary channels that create an electric field in the capillary channels to electrokinetically move substances in a fluid through the capillary channels. A method of using a microfluidic system having a plurality of electrodes, the method simultaneously controlling the time of application of an electrical parameter between at least three electrodes of the system to transfer a substance between the electrodes. Including the method. 5. The method of claim 4, wherein the application is controlled such that the substance migrates equivalently to the constant application of the electrical parameter between the electrodes of the system. 6. The method of claim 5, wherein the application is controlled by varying the percentage of time that the electrical parameter is applied. 7. The method of claim 4, wherein the electrical parameter comprises voltage. 8. The method of claim 4, wherein the electrical parameter comprises current. 9. The method of claim 4, wherein the electrical parameter comprises power. 10. A plurality of capillary channels on an insulating substrate and a plurality of electrodes on different nodes of the capillary channel, which create an electric field in the capillary channel to electrokinetically move a substance in a fluid through the capillary channel. A plurality of electrodes for biological flow and at least one electrically conductive lead on the substrate, the at least one electrically conductive lead extending to the capillary channel position, whereby the voltage at the capillary channel position can be determined. A microfluidic system comprising a conductive lead, the conductive lead having a width sufficiently small such that a voltage of less than 1 volt is created across the conductive lead at the capillary channel location. 11. The microfluidic system of claim 10, wherein the conductive leads have a width small enough so that a voltage of less than 0.1 volt is created across the conductive leads at the capillary channel locations. 12. The conductive lead is configured to form a voltage divider circuit on the substrate, the voltage received from the conductive lead being a portion of the voltage at the capillary channel location. The microfluidic system of claim 11. 13. An insulating plate overlying the substrate, the conductive leads extending to an edge of the substrate.
The microfluidic system of claim 10. 14. A substrate having a plurality of interconnected capillary channels, and a plurality of electrodes at different nodes of the capillary channel for creating an electric field in the capillary channel to create a substance in a fluid through the capillary channel. A plurality of electrodes for electrokinetic movement, and one or more power supplies connected to the plurality of electrodes, each of the one or more power supplies receiving a controllable reference voltage. A mixed block having one input terminal, a second input terminal and an output terminal; and a voltage amplifier connected to the output terminal of the mixed block and having first and second output terminals, The first output terminal is a voltage amplifier connected to at least one electrode, and a feedback block connected to the first output terminal of the voltage amplifier. Has an output terminal connected to an input terminal of the second of the mixing block further comprises a feedback block to stabilize the power supply to give a negative feedback, microfluidic systems. 15. The feedback block is connected to the first output terminal via a voltage divider circuit.
14. The microfluidic system according to 14. 16. The microfluidic system of claim 15, wherein the feedback block provides feedback to the mixing block in response to the voltage at the first output terminal. 17. The feedback block is connected to the second output terminal of the voltage amplifier, the feedback block being sourced or sunk through the first output terminal. In response to the amount of current, an output voltage is generated, the feedback block
16. The microfluidic system of claim 15, which provides feedback to the mixing block in response to the amount of current passed or reduced through the first output terminal. 18. The feedback block comprises a summing amplifier having a first input connected to the voltage divider circuit and a second input connected to the second output terminal of the voltage amplifier. The microfluidic system of claim 17, wherein the summing amplifier is responsive to the amount of current drawn or reduced through the first output terminal to generate the output voltage. 19. The feedback block is connected to the second output terminal of the voltage amplifier, the feedback block generating a first feedback voltage in response to a voltage at the first output terminal. A second feedback voltage is generated in response to an amount of current drawn or reduced through the first output terminal, and the feedback block is responsive to a control signal to the first or first and first feedback voltages. 16. The microfluidic system according to claim 15, comprising a switch for sending both two feedback voltages to the mixing block, so that the power supply is selectively regulated by voltage or current feedback, respectively. 20. Further comprising first and second buffer circuits connected to said feedback block,
The first buffer circuit may carry the first feedback voltage, the second buffer circuit may carry the second feedback voltage, and the first and second feedback voltages may be monitored. 20. The microfluidic system of claim 19. 21. The microfluidic system of claim 14, wherein the mixing block includes an operational amplifier connected as a summing amplifier. 22. The microfluidic power supply system of claim 21, wherein the operational amplifier is further connected as an integrator. 23. A power supply for connection to at least one electrode of a microfluidic system, the first input terminal for receiving a controllable reference voltage,
A mixing block having a second input terminal and an output terminal, and a voltage amplifier connected to the output terminal of the mixing block and having first and second output terminals, the first output terminal being A feedback block connected to the at least one electrode, a voltage amplifier connected to the first and second output terminals of the voltage amplifier, and the second input terminal of the mixing block, Generating a first feedback voltage in response to the voltage at the first output terminal and generating a second feedback voltage in response to the amount of current drawn or reduced through the first output terminal. A feedback block, the feedback block having a switch for sending the first or both first and second feedback voltages to the mixing block in response to a control signal. , Whereby the voltage or current of the power supply, respectively,
Selectively stabilized by negative feedback,
Power supply. 24. The power supply of claim 23, wherein the feedback block is connected to the first output terminal of the voltage amplifier via a voltage divider circuit. 25. The feedback block is connected to the second output terminal of the voltage amplifier, the feedback block responsive to an amount of current drawn or reduced through the first output terminal. 24. The power supply of claim 23, which produces an output voltage. 26. Further comprising first and second buffer circuits connected to said feedback block,
The first buffer circuit carries the first feedback voltage, the second buffer circuit carries the second feedback voltage, and the first and second feedback voltages may be monitored. The power supply according to claim 23. 27. The feedback block comprises a summing amplifier having a first input connected to the voltage divider circuit and a second input connected to the second output terminal of the voltage amplifier. 26. The power supply of claim 25, wherein the summing amplifier produces the output voltage in response to the amount of current drawn or reduced through the first output terminal. 28. The power supply of claim 23, wherein the mixing block includes an operational amplifier connected as a summing amplifier. 29. The power supply of claim 28, wherein the operational amplifier is further connected as an integrator. 30. A substrate having a plurality of interconnected capillary channels, and a plurality of electrodes at different nodes of the capillary channel, which create an electric field in the capillary channel to create a substance in a fluid through the capillary channel. A plurality of electrodes for electrokinetically moving the electrodes, and a plurality of power supplies connected to each of the electrodes, each of the power supplies supplying a selected voltage or a selected amount of current to the electrodes. To at least three of the electrodes in response to a current in at least two of the at least three electrodes.
A microfluidic system including a plurality of power supplies. 31. At least two intersecting channels.
using a substrate having ecting channels) by applying a voltage between the at least three electrodes in response to a current in at least two of the at least three electrodes associated with the target material. (Su
bject material) electrokinetically transported. 32. The substrate has a plurality of interconnected channels and associated electrodes that are in constant fluid communication with each other, wherein a voltage is applied to the electrodes in response to a current at the electrodes. 32. Use according to claim 31 for transporting a substance of interest along a predetermined path incorporating one or more of the channels. 33. Use of a substrate having at least two intersecting channels, by controlled and time-dependent and simultaneous application of electrical parameters between at least three electrodes associated with the channels. The use of electrokinetic transport. 34. The use according to claim 33, wherein the electrical parameter comprises voltage. 35. The use according to claim 33, wherein the electrical parameter comprises current. 36. The use according to claim 33, wherein the electrical parameter comprises power. 37. Use of an insulative substrate having a plurality of channels and a plurality of electrodes associated with the channels and at least one variable voltage controller operably connected to the plurality of electrodes, the controller comprising: The voltage applied to at least three electrodes of the plurality of electrodes is configured to be controlled in response to the magnitude of current in at least two electrodes of the at least three electrodes, and the voltage applied to the electrodes is controlled. Use, wherein the application causes an electric field in the channel to cause at least one conductive lead on the substrate to extend to the channel location, thereby determining an electrical parameter of the channel location. 38. The conductive lead has a width that is sufficiently small so that the conductive lead at the channel location
38. Use according to claim 37, which produces a voltage below volt, preferably below 0.1 volt. 39. A plurality of interconnected capillary channels and a plurality of electrodes at different nodes of the capillary channel, which create an electric field in the capillary channel to electrokinetically move a substance in a fluid through the capillary channel. A plurality of electrodes for moving electrokinetically, and a power supply connected to at least one of the electrodes, the first input terminal for receiving a reference voltage, the second input terminal, and the output terminal A power supply having a mixing block and connected to the output terminal of the mixing block,
A voltage amplifier having first and second output terminals, the first output terminal being connected to the at least one electrode, and the voltage amplifier being connected to the first output terminal of the voltage amplifier. The use of an insulating substrate having a feedback block having an output terminal connected to the second input terminal of the mixing block and providing negative feedback to stabilize the power supply. 40. The feedback block is also connected to the second output terminal of the voltage amplifier, the feedback block generating a first feedback voltage in response to a voltage at the first output terminal. And generating a second feedback voltage in response to an amount of current drawn or reduced through the first output terminal, the feedback block responsive to a control signal to the mixing block. 40. The use according to claim 39, comprising a switch for delivering one or a second feedback voltage, whereby the power supply is selectively regulated by voltage or current feedback. 41. Use of a power supply for connecting to at least one electrode of a microfluidic system, the power supply comprising a first input terminal for receiving a reference voltage, a second input terminal, and an output. A voltage amplifier having a mixed block having a terminal and first and second output terminals connected to the mixed block output terminal, the first output terminal being connected to the at least one electrode And a feedback block connected to the first and second output terminals of the voltage amplifier and the second input terminal of the mixing block, the feedback block comprising a voltage at the first output terminal. Generating a first feedback voltage in response to the first feedback voltage and generating a second feedback voltage in response to the amount of current drawn or reduced through the first output terminal. Back block in response to the control signal, the first or the second feedback voltage a switch to send to the mixing block, whereby,
Use, wherein the power supply is selectively regulated by negative feedback. 42. A substrate is a plurality of interconnected capillary channels and a plurality of electrodes at different nodes of the capillary channel that create an electric field in the capillary channels to create a substance in a fluid through the capillary channels. A plurality of electrodes for electrokinetically moving the electrodes, and a plurality of power supplies connected to each of the electrodes, each of the power supplies supplying a selected voltage and a selected amount of current to the electrodes. Of at least three of the electrodes, and a plurality of power supplies capable of selectively supplying in response to a current of at least two of the at least three electrodes. 43. A substrate having at least two interconnected channels that electrokinetically transport a substance of interest, means for measuring an electric current, and at least 3 associated with the channels.
Means for applying a voltage between said at least three electrodes in response to an electric current in at least two of said electrodes. 44. The substrate has a plurality of interconnected channels and associated electrodes that are in constant fluid communication with each other, the voltage being applied to the electrodes in response to a current at the electrodes. 44. The system of claim 43, which transports a substance of interest along a predetermined path that incorporates one or more of the channels. 45. Controlled and time-dependent and simultaneous application means of electrical parameters between a substrate having at least crossed channels for electrokinetic transport of a substance of interest and at least three electrodes associated with the channels. A microfluidic system, including and. 46. The system of claim 45, wherein the electrical parameter comprises voltage. 47. The system of claim 45, wherein the electrical parameter comprises current. 48. The system of claim 45, wherein the electrical parameter comprises power. 49. An insulating substrate having a plurality of channels and a plurality of electrodes associated with the channels, means for generating an electric field in the channels by applying a voltage to the electrodes, and an electrical parameter of the channel position. A microfluidic system comprising at least one conductive lead on the substrate extending to a channel location so that it can be determined, wherein the means for generating the electric field is operatively connected to the plurality of electrodes. At least one variable voltage controller for controlling an applied voltage to at least three electrodes of the plurality of electrodes in response to a magnitude of a current at at least two electrodes of the at least three electrodes. The microfluidic system including the configured controller. 50. The conductive lead has a width that is sufficiently small so that the conductive lead at the channel location
50. The system according to claim 49, which produces a voltage below volt, preferably below 0.1 volt.